1. Field of the Invention
This invention relates to a semiconductor chip with a circuit connected to an oscillator to generate clocks, and a semiconductor integrated circuit with the semiconductor chip sealed in a package.
2. Description of the Related Art
In a semiconductor integrated circuit including a circuit to generate an oscillating wave by means of connecting an oscillator outside between an input and an output terminals, it is known to be effective for lightening the hindrance in oscillation such as an parasitic oscillation or the like to shorten the wiring length as much as possible between the oscillator and the semiconductor integrated circuit, and to ground or shield the vicinity of the input and the output terminals by a ground earth wire of low impedance disposed between the terminals. However, the input and the output terminals to the oscillator are provided too close to each other in a conventional semiconductor integrated circuit.
FIG. 1 is a partial plan view showing the periphery of an oscillating circuit of a conventional semiconductor integrated circuit. In the figure, a numeral 1 denotes a semiconductor chip 1 which has an input electrode 4 for inputting an oscillating waveform from an oscillator 8a and an output electrode 6 for supplying a voltage to oscillate the oscillator 8a. The semiconductor chip 1 is fixed to a frame 3 of the ground potential and sealed in a package 2. The package 2 has an input terminal 5 and an output terminal 7 to be respectively connected with the input electrode 4 and the output electrode 6 of the semiconductor chip 1 via metallic wires.
An output and an input terminal of the two-terminal oscillator 8a are connected via capacitors 9, 9 for reducing harmonic noises in the oscillating waveform to the corresponding input terminal 5 and output terminal 7 of the package 2 by wire patterns formed on a wiring substrate 12. A ground wire pattern 14 to shield between the input terminals and output terminals is formed between the above wire patterns for connecting the input and the output terminals 5 and 7 with the input and the output terminals of the oscillator 8a.
FIG. 2 is a partial plan view showing the periphery of an oscillating circuit of a conventional semiconductor integrated circuit to which a three-terminal oscillator with a capacitor incorporated is connected. In the drawing, references 10 and 8b represent a semiconductor integrated circuit and a three-terminal oscillator, respectively. Generally, the central terminal of the oscillator 8b is a connecting terminal to the ground potential, and the output and the input terminals located on both sides of the connecting terminal are connected to the input and the output terminals 5 and 7, respectively of the semiconductor integrated circuit.
In the conventional semiconductor integrated circuits in the above-described structure, the wire pattern on the wiring substrate is inevitably bent in the vicinity of the oscillator, thus causing the wiring length to be elongated and to increase the wiring area, since the input and the output terminals are arranged adjacent to each other, and moreover, since the interval of the terminals becomes narrower according to the recent trend of higher integration of the circuit.
Further, although it is generally ideal that the ground wire has a low impedance, the wiring width of the ground wire pattern 14 is too narrow to obtain enough ground effect because the space between the input and the output terminals 5 and 7 is narrow. At the same time, the narrow space hinders ground within the package between the input and the output terminals 5 and 7.
If an ground wire is provided between the input and the output terminals 5 and 7 of the semiconductor integrated circuit connected with a three-terminal oscillator, the ground effect cannot be expected so much as above due to the narrow wiring width. In this case, therefore, the central ground terminal of the oscillator is connected to a wire of the ground potential pulled from the other surface or from the other wiring layer of the wiring substrate. Further, the oscillator is necessary to be separated by a predetermined distance from the semiconductor integrated circuit in order to wire between the input terminal and the output terminal of the oscillator and the semiconductor integrated circuit in a manner not to overlap the ground terminal of the oscillator. As a result, the wiring length becomes longer thereby to increase the wiring area.